For the separation of particles from large flows of gas, various types of centrifugal separator are currently used. For example, WO 01/36103 and U.S. Pat. No. 3,234,716 describe centrifugal separators for cleaning gases containing particles, such as oil particles, dust, etc., where the separator comprises a rotor mounted in a stationary casing in such a way that it can rotate, with a stack of surface elements in the form of, for example, conical sedimentation plates (insert plates). Separators of this type are effective for the separation of particles within a wide range of particle sizes. This is due to the short sedimentation distances between the plate elements and the high centrifugal forces. This type of separator is suitable for handling large quantities of particles. However, in certain applications they can be less effective, for example for the separation of the very smallest and lightest particles in the flow of gas, for example particles smaller than approximately 1 μm. These extremely small and light particles are thus often able to pass through the rotor's plate stack without being deposited on the surface elements and on the inside of the surrounding casing, with the result that these particles pass out of the separator along with the gas, without being separated off.
In order to separate off extremely small and light particles from flows of gas, electrostatic filters or cleaners can be used, which, however, have limitations when it is a question of separating larger particles and handling larger quantities of particles.
In order to be able to separate off both very small, light particles and also larger, heavier particles from flows of gas, various types of electrostatic filter or cleaner have previously been proposed, using which it is possible to separate off the fine particles from the gas by means of a combination of electrostatic forces and centrifugal forces. For example, GB 729 612, U.S. Pat. Nos. 2,853,151 and 4,718,923 describe various types of such electrostatic separators, where the particles in the flow of gas are charged and at the same time the flow of gas is subjected to a cyclone effect in order to separate off small and large particles by means of the centrifugal forces. A disadvantage with these separators is that the charged surfaces, on which particles are deposited, are stationary and quickly become coated to such an extent that the electrostatic forces are ineffective. Accordingly, such separators cannot handle flows of gas with a high particle content.